Long-Haul Dense Wave Division Multiplexing (DWDM) transport is expected to be the dominant cost and limiting contributor of an end-to-end link for many years to come. There is momentum in the industry to define a flexible end-to-end packet flow with a flexible Ethernet architecture to adapt to line capabilities. A consortium of companies is defining a Physical Coding Sublayer (PCS) layer Flexible Ethernet (FlexE) scheme based on a generalized approach resembling the Optical Internetworking Forum (OIF) Multi Link Gearbox (MLG) extensions utilizing granularity of PCS lanes (e.g., 5 Gb/s) and Physical Medium Dependent (PMD) (e.g., 100GBASE-SR4). For example, this Flexible Ethernet MAC proposal is described by Xiaoxue Zhao et al., “The Prospect of Inter-Data-Center Optical Networks,” IEEE Communications Magazine, September 2013, the contents of which are incorporated by reference herein. The FlexE scheme is also referred to as a “shim” PCS function. There are currently no defined and standard schemes for mapping this FlexE to OTN. Transport gear needs to solve this problem in an efficient manner. OIF MLG extensions are described in OIF IA # OIF-MLG-02.0 Multi-link Gearbox Implementation Agreement, April 2013, available online at www.oiforum.com/public/documents/OIF-MLG-02.0pdf, and the contents of which are incorporated by reference herein.
Conventionally, there are two standard mapping procedures that could be applicable to FlexE, namely Optical channel Data Unit (ODU) flex (ODUflex) Constant Bit Rate (CBR) and ODUflex Generic Framing Procedure (GFP). ODUflex(CBR) mapping requires logic to bit-demultiplex, Forward Error Correction (FEC) decode (possibly), align, reorder and deskew PCS Virtual Lanes (VLs) with knowledge of grouping and VL sizes. There could be multiple PCS/FlexE per PMD/port or vice-versa. This is a PCS layer type of mapping in transport gear and has cost/logic associated with the implementation. ODUflex(GFP) mapping requires logic to bit-demultiplex, FEC decode (possibly), align, reorder and deskew PCS VLs, then terminate the PCS coding (64B/66B) with knowledge of groupings to get to packet or MAC layer in order to perform Frame mapped GPF (GFP-F) mapping. There could be multiple FlexE per PMD/port or vice-versa. This is a Media Access Control (MAC)/packet layer type of mapping in transport gear and has significant cost/logic associated with the implementation.